With its spacious, tree-lined grounds and slightly threadbare classrooms, there is nothing obviously unusual about the Kampang Secondary School.

It is situated in Thailand's impoverished north-east, and most of the pupils are the children of farmers.

Every morning at 0800 they all gather outside to sing the national anthem and watch the flag being raised.

Then they have a chance to use the toilets, before heading off the first classes of the day.

Kampang is proud of its toilets. Spotless, and surrounded by flowering tropical plants, they have won national awards for cleanliness.

But there is something else about them too. Between the girls' toilet and the boys', there is one signposted with a half-man, half-woman figure in blue and red.

This is the transsexual toilet, and outside, in front of the mirrors, some decidedly girly-looking teenage boys preen their hair and apply face cream.

'Uncomfortable'

The headteacher, Sitisak Sumontha, estimates that in any year between 10% and 20% of his boys consider themselves to be transgender - boys who would rather be girls.

"They used to be teased every time they used the boys' toilets," he said, "so they started using the girls' toilets instead. But that made the girls feel uncomfortable. It made these boys unhappy, and started to affect their work."

So the school offered to build the transgender boys their own facility, and they welcomed it.

Triwate Phamanee is a slightly built 13-year-old who is adamant that he will one day change his gender.

"We're not boys," he told me, "so we don't want to use the boys' toilet - we want them to know we are transsexuals."

Vichai Saengsakul, 15, agrees.

"People need to know that being a transsexual is not a joke," he says, "it's the way we want to live our lives. That's why we're grateful for what the school has done."

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What the third toilet looks like

Normal treatment

The transgender boys in Kampang tend to stick together as a group, practising their somewhat exaggerated feminine mannerisms together and generally camping it up.

They still have to wear male uniforms, make-up is not allowed (although some manage to sneak in a touch of lipstick and mascara), and of course sex-change surgery is out of the question at this age - the youngest self-declared transsexual is 12.

But they appear to be treated perfectly normally by other pupils and teachers alike.

I asked the headmaster whether they were not too young to be making decisions about their gender.

He said that, in his 35 years of working in the Thai education system, he had come across many boys like this, and they never changed. Many go on as adults to have sex-change surgery, while others will live as gay men, he said.

Thailand is well known for its tolerance of transgender men, and they are very visible in everyday life. Sex-change surgery has become a speciality of the Thai health industry, and it is relatively inexpensive; patients come here from all over the world for the operation.

'Sweet and soft'

The Kampang school's initiative, far from stirring up controversy, has instead prompted a discussion in other schools over whether they should be providing the same facilities.

A ratio of 10% to 20% of boys calling themselves transsexual in a provincial high school does seem very high, but Mr Sitisak assured me that in his experience it was not unusual.

Which brought up a question that has been rattling around my head ever since I first lived in Thailand seven years ago: Why do so many Thai men want to become women?

I asked Suttirat Simsiriwong, who became a campaigner for transgender rights after she was barred entry to a nightclub at an international hotel in Bangkok last year.

Poised, articulate and very feminine, it is hard to tell that she was not born a woman.

"Maybe the numbers of gays, of people with sexual identity issues, might be the same as in other countries," said Suttirat, "but because Thai society and culture tend to be very sweet, very soft, and the men can be really feminine, if we tend to be gay, many of us tend to be transgender."

So does building a special toilet in school advance the cause of winning wider acceptance for transsexuals?

"At that age it's good for them to have a specific place," she said.

"But when they graduate from school or university, they will know how to have medical treatment. They won't want to go into a transgender toilet because they will want to be accepted as a woman - so they will go to the women's toilet."

Discrimination remains

Tolerance, said Suttirat, is not the same thing as acceptance.

Despite their high profile in Thailand, transsexuals complain that they are still stereotyped - they can find work easily enough as entertainers, in the beauty industry, the media, or as prostitutes, but it is much harder to become a transgender lawyer or investment banker.

And their biggest complaint is that they cannot change their legal status.

Despite a proposal during the drafting of a new constitution last year, to allow them to change the gender on their identity cards, this has not yet been approved.